@riot serious question about balance choices

How do you guys actually decide what to work on? I see all these newer champs or champs that have recently been reworked come out and be really good and then they are played a ton and considered really strong. Then you nerf them and almost immediately rebuff them when they fall even slightly out of favor. Yet you can't even make the smallest change to a champion like nidalee so that she isn't terrible in lane. What's going on? Are we going to have to wait for all the older champions to get reworks before they see any love or what?